AERIAL ELECTROMAGNETIC MAPPING (AEM)
Gisborne Aerial Electromagnetic Mapping (SkyTEM)
The Aerial Groundwater Mapping project is a scientific investigation to find out more information on the aquifer systems in Tairāwhiti/Gisborne. Aerial mapping of aquifers was undertaken using a helicopter in January 2024. Surveys were completed in Wharekahika (Hicks Bay), Te Araroa, Waiapu, Tolaga, and across Poverty Bay flats. See below for a map that details the project boundaries.
Who is supporting the mahi
The project has formed from collaboration between AIA and Gisborne District Council, in discussion with iwi. The $1.8 million project is largely funded through Aqua Intel Aotearoa, with Gisborne District Council meeting the costs of aerial mapping on the East Coast.
The project has been planned in discussion with Te Runanganui o Ngāti Porou, Tāmanuhiri Tūtū Poroporo Trust, Te Aitanga a Māhaki Trust, and Rongowhakaata Iwi Trust. All four iwi have indicated they support the objective of gathering scientific information to guide decision making. Iwi are involved in finalising data management and governance arrangements for accessing, storing and using the data for future purposes.
Project status
Helicopter flights were completed in February 2024, following delays related to Cyclone Gabrielle. GNS scientists have begun the work of analysing the data. Meanwhile, discussions are underway with iwi, hapū, and landowners on arrangements for accessing, storing and using the data after it has been used to set water allocation policies and limits. Aqua Intel Aotearoa has presented very early high-level findings about the shallow nature of the East Coast aquifers to local groups and to the council. The work to develop and interpret resistivity models to understand the characteristics of the aquifers will continue until early 2025. This will include mapping locations of saline groundwater, classifying the geological formations based on their water storage and transmission capacity, and identifying shallow features. These elements will be combined together to create an overall 3D subsurface picture.
Following this work, the council will update its modelling to incorporate the AEM results. The models will then inform the process of setting water allocation policies and limits for Gisborne.
What we want to learn
We will never know everything about the aquifer, but this study will give us a better understanding of:
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what the aquifer looks like (e.g. depth, extent, geology)
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how the aquifer is connected to wetlands, lakes and streams
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the relationship between shallow (unconfined) and deeper (confined) aquifer systems
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the boundary between the aquifer and seawater (seawater intrusion risk)
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how groundwater recharges.
Northern Tairāwhiti aquifer survey update [June 2024]
The northern Tairāwhiti survey was part of a Government and Gisborne District Council (GDC) funded scientific project, supported by Ngati Porou, to understand more about how water is stored in underground aquifers across the region. It covered areas around Wharekahika/Hicks Bay, Te Araroa, Waiapu and Tolaga Bay. GDC and Ngati Porou want better information for communities to use in making decisions about the use of water.
Overview
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He taonga te wai. Water is precious. Despite this we don’t know enough about how much we have or where it is.
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The first results from a survey of northern Tairāwhiti underground aquifers indicate the aquifers are shallow, suggesting limits on the amount of water that may be available for day to day use in future.
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Careful management of East Coast aquifers will be necessary to protect groundwater for future generations and to ensure the ongoing health of waterways.
Information gathering
The Aerial electromagnetic (AEM) surveying involved flying over the land with a loop system suspended from a helicopter. Transmitters on the loop send electromagnetic signals underground, and sensors measure the behaviour of the returning signals. This provides data about the resistivity of the ground; that gives us information about rock type, porosity, permeability, clay content, moisture content, and other properties. GNS scientists analyse and interpret the raw data and combine it with other information, such as data from groundwater bores, to create 3D aquifer maps and models.
Figure 1: Photograph of the local community and the SkyTEM Helicopter during the aerial survey.
Early indications
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GNS has undertaken an initial review of the results from the survey, essentially a ‘first look’ at the data files.
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This indicates the northern Tairāwhiti area has shallow ground water resources compared to other New Zealand regions.
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This is consistent with other existing information about this area, where wells have been known to run dry at times.
Detailed interpretation and analysis 2024 – 2025
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There is a lot more work to be done by GNS scientists to build a more complete picture.
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Detailed reports will be provided to inform the freshwater and catchment planning process underway in Tairāwhiti.
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Raw data will be managed in line with principles currently under discussion with iwi and hapū.
Link to a recent news article: https://www.nzherald.co.nz/nz/new-survey-shows-limited-water-availability-on-east-coast/NCLSQLP5AVEGPCV2QOBMCIXAQE/
Tairāwhiti aquifer mapping project features on Ngati Porou Radio [25/02/2024]
Skip to 3 min 15 sec for a summary of the aquifer mapping project.
Frequently asked Questions
Click the link to navigate to our Aerial Electromagnetic Mapping Frequently Asked Questions Page
How to find out more:
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Read the FAQ's about AEM on our website here
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Phone Gisborne District Council: 0800 653 80
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Email Aqua Intel Aotearoa: info@aquaintel.co.nz
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Email Gisborne District Council: customer.service@gdc.govt.nz
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Use the form at the bottom of the page to send an enquiry.
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Visit our Facebook page.
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Download our Project Factsheet
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Check out our Public Flyer
